Alcoholic hepatitis is a leading cause of liver disease and death worldwide; thus, there is an urgent need to develop novel therapeutic interventions. Key events for the onset and progression of alcoholic hepatitis result from the gut-to-liver interaction. Vitamin D deficiency is highly prevalent in patients with alcoholic hepatitis. VitaminD supplementation regulates the expression of tight junction proteins, enhances antimicrobial defenses and reduces proinflammatory cytokines in the gut. Vitamin D targets osteopontin via a vitamin D-responsive element in the osteopontin promoter. Milk osteopontin protects the gut by maintaining the epithelial barrier function, providing mucosal defense, preventing sepsis and the inflammatory response. So far, a link between vitamin D and osteopontin in protecting from alcoholic hepatitis has not been established. We believe that nutritional therapy using vitamin D and milk osteopontin could protect from alcohol-induced liver injury. In this Application we will focus on testing the Central Hypothesis Dietary supplementation with vitamin D or milk osteopontin could prevent alcoholic hepatitis due to the gut protective and antisteatotic actions of osteopontin. In particular, we hypothesize that vitamin D and milk osteopontin will: 1) Target the gut-liver axis protecting the intestinal mucosal barrier and blocking the translocation of Gram-negative bacteria from the gut into the portal circulation thus lowering lipopolysaccharide levels; 2) Prevent steatosis and liver injury by targeting fatty acid metabolism and decreasing lipopolysaccharide-mediated Kupffer cell activation and TNF production; and 3) Avert hepatic steatosis, inflammation and liver injury by increasing autophagy, a recently identified pathway regulating steatosis. We will develop new in vivo models of alcoholic hepatitis to further our understanding of the mechanisms of liver injury. Using these models, mice will be treated with vitamin D or milk osteopontin to assess their therapeutic potential. To prove our hypothesis we plan three Specific Aims. In Aim 1, we will analyze if vitamin D and milk osteopontin block the ethanol-mediated increase in gut permeability, bacterial translocation and lipopolysaccharide availability. The chronic Lieber-DeCarli model along with dextran sodium sulfate treatment will be used. In Aim 2, first, we will determine whether vitamin D and milk osteopontin blunt steatosis by targeting fatty acid metabolism; and second, we will dissect if the ability of osteopontin to bind lipopolysaccharide lowers Kupffer cell activation, TNF production as well as other pro-inflammatory cytokines. The chronic Lieber-DeCarli model along with dextran sodium sulfate or lipopolysaccharide treatment will be used. In Aim 3, a new model of alcoholic hepatitis based on autophagy blockade will be developed. Next, we will identify if vitamin D and milk osteopontin reduce steatosis by activating the autophagy pathway independent of targeting bacterial translocation or binding lipopolysaccharide. Thus, the Overall Goal of this Application is to investigate whether dietary administration of vitamin D and milk osteopontin could be an efficient low-cost therapeutic strategy for slowing down or preventing the progression of alcoholic hepatitis.